Whatever it is, boy is it very comfortable. I got this top from the sale bin at Eairth a couple of months ago and haven't really gotten to wear it out until today. The curved hem and the unusual stitching done on the edges (which you really can't see, can you) keeps it from looking like I just wore a regular t-shirt in the largest size possible, I think.
Eairth big t-shirt, tailor-made black skinnies, Zara shoes
I've definitely gone a complete 180 since my days of wearing fitted shirts with elephant pants in the 90's. This shirt goes down my list of comfy things to wear on a plane.